I. Field of the Invention
The present invention relates to wireless data services. More particularly, the present invention relates to a novel and improved method and system for performing proxy mobile node registration of a terminal device requesting IP mobility support.
II. Description of the Related Art
Internetworking, i.e., the connection of individual local area networks (LANs), has rapidly become very popular. The infrastructure and associated protocols commonly referred to as the "Internet" have become well known and widely used. At the heart of the Internet is the Internet Protocol (IP) which supports the routing of datagrams between the LANs as is well known in the art, and further described in Request For Comment (RFC) 791 entitled, "INTERNET PROTOCOL DARPA INTERNET PROGRAM PROTOCOL SPECIFICATION," dated September 1981.
IP is a datagram-oriented protocol which provides several services, including addressing. The IP protocol encapsulates data into an IP packet for transmission, and affixes addressing information to the header of the packet. IP headers contain 32-bit addresses that identify the sending and receiving hosts. These addresses are used by intermediate routers to select a path through the network for the packet towards its ultimate destination at the intended address. A basic concept of IP addressing is that initial prefixes of the IP address can be used for generalized routing decisions. For example, the first 16 bits of an address might identify Qualcomm, Inc., the first 20 bits identify the Qualcomm's main office, the first 26 bits identify a particular Ethernet in that office, and the entire 32 bits identify a particular host on that Ethernet. As a further example, every address in Qualcomm's IP network might be of the form (in "dotted-quad notation"): 129.46.xxx.xxx, where "xxx" refers to any allowable integer between zero and 255.
As is evident by this prefix-based routing characteristic of IP, the IP addresses contain implied geographical information about the location of a particular host on the Internet. In other words, whenever any router on the Internet receives a packet having a destination IP address that begins "129.46" the router forwards that packet in a particular direction towards the Qualcomm, Inc. network in San Diego, Calif., USA. Thus, the IP protocol allows datagrams originating at any Internet node in the world to be routed to any other Internet node in the world, given that the originating party knows the IP address of the destination party.
As mobile computing and mobile Internet access have grown in popularity, a need has arisen to provide mobile data support for mobile terminals such as laptop or palmtop computers using the IP protocol. However, as just mentioned, the IP addressing scheme used for Internet routing contains implied geographic information. In other words, if a user desires to use a fixed IP address to identify his mobile terminal, the IP packets intended for that mobile terminal will not be routed to that mobile terminal when it is away from its "home" network (i.e., the network which encompasses its fixed IP address) in the absence of some technique for "forwarding" IP packets to the mobile terminal.
For example, suppose a user decides to remove his mobile terminal from its "home" IP network at Qualcomm, Inc. in San Diego, and take it with him on a trip to Palo Alto, Calif., and there connect to Stanford University's IP network while still keeping his Qualcomm-assigned fixed IP address. Any IP datagram intended for the mobile terminal will still be routed to Qualcomm's IP network because of the geographical location information implicit in the mobile terminal's fixed IP address. Such IP packets will not be delivered to the mobile terminal while away from its "home" network unless some mechanism is in place to forward IP packets from Qualcomm's IP network to the mobile terminal at its current point of attachment to the Internet at Stanford University's IP network in Palo Alto.
In order to meet this need, RFC 2002, entitled "IP Mobility Support," dated October 1996, specifies protocol enhancements that allow transparent routing of IP datagrams to mobile nodes in the Internet. Using the techniques described in RFC 2002, each mobile node may always be identified by its "home" IP address, regardless of its current point of attachment to the Internet. While situated away from its home IP network, a mobile terminal may become associated with a "care-of" address, thereby providing forwarding information necessary to route IP datagrams to its current point of attachment to the internet. RFC 2002 accomplishes this by providing for registration of the care-of address with a "home agent." This home agent forwards IP datagrams intended for the mobile terminal by using a technique called "IP tunneling." IP tunneling involves the home agent attaching a new IP header which contains the care-of address to any arriving IP packet which has a destination address corresponding to the mobile terminal's home IP address. After arriving at the care-of address, a "foreign agent" at the care-of address strips off the IP tunneling header, and delivers the IP packet to the mobile terminal at its current point of attachment to the internet.
In this way, the techniques of RFC 2002 provide mobile data services for users who desire to relocate their mobile terminal's point of attachment to the internet without having to change the mobile terminal's IP address. This ability has several advantages. First, it allows originating nodes elsewhere on the Internet to send periodic "push" services to the mobile terminal regardless of where it is. Such services might include stock quotes or e-mail. This obviates the need for the mobile user to "dial in" or otherwise contact his home network in order to retrieve information. Furthermore, it allows the mobile terminal to relocate as often as desired, without any originating parties having to keep track of where the mobile terminal is currently located.
To increase the freedom of mobility of the mobile terminal, many mobile users will typically use wireless communication devices, such as cellular or portable phones, to connect to the Internet. In other words, many mobile users will use wireless communication devices, commonly referred to as "mobile stations," or MT2 devices, as the point of access to the land-based network. As used herein, "mobile station" or "MT2 device" will refer to any subscriber station in the public wireless radio network that is intended to be used while in motion or during halts at unspecified points. Mobile stations and MT2 devices include portable units (e.g., hand-held personal phones) and units installed in vehicles, as well as wireless local loop (WLL) telephones.
FIG. 1 illustrates a high-level block diagram of a wireless data communication system in which a mobile terminal (TE2 device) 102 communicates with an Interworking Function (IWF) 108 via a wireless communication system which includes wireless communication device (MT2 device) 104 and Base Station/Mobile Switching Center (BS/MSC) 106. In FIG. 1, the IWF 108 serves as the access point to the Internet. IWF 108 is coupled to, and often co-located with BS/MSC 106, which may be a conventional wireless base station as is known in the art. TE2 device 102 is coupled to MT2 device 104, which is in turn in wireless communication with BS/MSC 106 and IWF 108.
Many protocols exist which allow data communication between the TE2 device 102 and the IWF 108. For example, Telecommunications Industry Association (TIA)/Electronics Industries Association (EIA) Interim Standard IS-707.5, entitled "Data Service Options for Wideband Spread Spectrum Systems: Packet Data Services," published February 1998, defines requirements for support of packet data transmission capability on TIA/EIA IS-95 wideband spread spectrum systems, of which BS/MSC 106 and IWF 108 may be a part. IS-707.5 specifies a packet data bearer service that may be used for communication between TE2 device 102 and IWF 108 via BS/MSC 106. It provides procedures that can apply to multiple packet data services, including the Mobile IP service of RFC 2002, as well as Cellular Digital Packet Data (CDPD) which is described in CDPD-1995, entitled "Cellular Digital Packet Data System Specification, Version 1.1," published Jan. 29, 1995 by the CDPD Forum, Inc.
CDPD is an AMPS (analog) cellular data service, which includes some of its own support for mobility. CDPD differs from Mobile IP in several significant ways. Most notably, a CDPD modem has an assigned IP address that belongs to the CDPD network. So although a CDPD modem may roam within the CDPD network, it may not use its IP address outside of the CDPD network in the same way that a Mobile IP supported terminal may use its "home" IP address outside of its "home" network.
IS-707.5 also provides the requirements for communication protocols on the links between TE2 device 102 and the MT2 device 104 (the R.sub.m interface), between the MT2 device 104 and the BS/MSC 106 (the U.sub.m interface), and between the BS/MSC 106 and the IWF 108 (the L interface).
Referring now to FIG. 2, a diagram of the protocol stacks in each entity of the IS-707.5 Relay Model is shown. FIG. 2 corresponds roughly to FIG. 1.4.2.1-1 of IS-707.5. At the far left of the figure is a protocol stack, shown in conventional vertical format, showing the protocol layers running on the TE2 device 102 (e.g., the mobile terminal, laptop or palmtop computer). The TE2 protocol stack is illustrated as being logically connected to the MT2 device 104 protocol stack over the R.sub.m interface. The MT2 device 104, is illustrated as being logically connected to the BS/MSC 106 protocol stack over the U.sub.m interface. The BS/MSC 106 protocol stack is, in turn, illustrated as being logically connected to the IWF 108 protocol stack over the L interface.
An example of the operation of FIG. 2 is as follows. An upper layer protocol 202 entity, such as an application program running on the TE2 device 102 has a need to send IP packets over the Internet. An example application may be a web browser such as Netscape Navigator, or Microsoft Internet Explorer, or the like. The web browser requests a Universal Resource Locator (URL), such as http://www.qualcomm.com. A Domain Name System (DNS) protocol, also in the upper layer protocols 202, translates the textual host name www.qualcomm.com to a 32-bit numeric IP address. The Hypertext Transfer Protocol (HTTP), also an upper layer protocol 202, constructs a GET message for the requested URL, and also specifies that Transmission Control Protocol (TCP) will be used to send the message and that TCP port 80 is used for HTTP operations.
The TCP protocol, also an upper layer protocol 202, opens a connection to the IP address specified by DNS, port 80, and transmits the HTTP GET message. The TCP protocol specifies that the IP protocol will be used for message transport. The IP protocol, a network layer protocol 204, transmits the TCP packets to the IP address specified. The Point to Point Protocol (PPP), a link layer protocol 206, encodes the IP/TCP/HTTP packets and transmits them across the R.sub.m interface using the relay layer protocol 208 EIA-232 to the EIA-232-compatible port on the MT2 device. The PPP protocol is described in detail in RFC 1661, entitled "The Point-to-Point Protocol (PPP)."
The EIA-232 protocol 210 on the MT2 device 104, passes the transmitted PPP packet to a combination of the Radio Link Protocol (RLP) 212 and IS-95 protocol 214 for transmission to the BS/MSC 106 over the U.sub.m interface. The RLP protocol 212 is defined in IS-707.2, and the IS-95 protocol is defined in IS-95 mentioned above. A complementary relay layer protocol stack on the BS/MSC 106, including a combination of RLP protocol 216 and IS-95 protocol 218 receives the PPP packets over the U.sub.m interface, and passes them to the MT2 relay layer protocol 220 for the L interface to the IWF relay layer protocol 228. The MT2 relay layer protocol 220 and the IWF relay layer protocol 228 are described in TIA/EIA IS-658 entitled, "Data Services Interworking Function Interface Standard for Wideband Spread Spectrum Digital Cellular System."
The PPP protocol 226 in the link layer of the IWF decodes the PPP packets from the TE2 device 102, and serves to terminate the PPP connection between the TE2 device 102 and the IWF 108. The decoded packets are passed from the PPP protocol 226 to the IP protocol in the network layer protocols 224 of the IWF 108 for examination, and further routing to the IP address specified by the TE2 device 102 in the IP packet header (here, the IP address for www.qualcomm.com). If there are any upper layer protocol tasks to be performed at the IWF 108, such as TCP, they are performed by the upper layer protocols 222.
Assuming that the ultimate destination of the IP packets generated by the TE2 device 102 is not the IWF 108, the packets are forwarded through the network layer protocols 224, PPP protocols 226 and relay layer protocols 228 of the IWF 108 to the next router (not shown) on the Internet. In this manner, IP packets from the TE2 device 102 are communicated through the MT2 device 104, the BS/MSC 106, and the IWF 108 towards their ultimate intended destination on the Internet, thereby providing wireless packet data services for the TE2 device 102 according to the IS-707.5 standard relay model.
As illustrated in FIG. 2, the IS-707.5 standard provides the requirements for communication protocols on the links between a TE2 device 102 and an IWF 108, including the requirements for the R.sub.m, the U.sub.m, and the L interfaces. These requirements and procedures are applicable to supporting the Mobile IP services described in RFC 2002. However, IS-707.5 does not provide procedures for establishing Mobile IP services in the first instance. In other words, IS-707.5 provides a framework for supporting Mobile IP services, but does not provide procedures for negotiating Mobile IP services, or registering the TE2 device 102 with a home agent and a foreign agent for Mobile IP services. These procedures are found in RFC 2002 itself.
This distinction is important when one considers that typically some application layer entity must therefore exist in the TE2 device 102 to support Mobile IP. Unfortunately, the most popular operating system software for personal computing, Microsoft Windows, does not have support for Mobile IP, and is currently not forecast to have such support. As a result, TE2 devices running Microsoft Windows (or one of many other operating systems) are not able to use their "home" IP address when they are not connected to their "home" IP network. This prevents the mobile user from taking advantage of the benefits of Mobile IP services like "push" services and direct e-mail delivery while away from the "home" IP network.
What is needed is a method and system for performing Mobile IP registration of a TE2 device, with the MT2 device acting as a proxy for the TE2 device in order to establish Mobile IP support for the TE2 device.